The defender is closing in on a return to full fitness but may not be risked for the opening Bundesliga game of the season
The centre-back enjoyed an extended break after winning the World Cup with Germany this summer but is not yet 100% fit, and Klopp keen to avoid rushing him back too soon.
He told reporters: "Mats needs a bit more training and he will get it. His position is the least of our worries at the moment."
Dortmund are without 10 first team players for the clash against Leverkusen after injury problems blighted their bid to battle Bayern Munich for the Bundesliga last season.
Oliver Kirch, Dong-Won Ji, Marcel Schmelzer, Nuri Sahin, Jakub Blaszczykowski, Adrian Ramos, Ilkay Gundogan, Erik Durm and Roman Weidenfeller all absent.
However, new signings Ciro Immobile and Matthias Ginter will start and Klopp is remaining optimistic over their opening game of the season.
"Bayer have always had quality and they've strengthened again," he added.
"They've been awkward opponents over the past few years, but then again so have we. The key question is not 'who has come through pre-season really well, but who is able to harm them the most?'"